


pampinus

by armethaumaturgy



Category: Undertale (Video Game)
Genre: Explicit Sexual Content, Killer (Killertale) - Freeform, M/M, Nightmare (Dreamtale) - Freeform, Oral Sex, Sounding, Tentacle Sex, Tentacles, Throne Sex, Vaginal Sex, killermare - Freeform, peace signs and fades out
Language: English
Status: Completed
Published: 2021-01-19
Updated: 2021-01-19
Packaged: 2021-03-17 19:46:59
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,840
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28854537
Author URL: https://archiveofourown.org/users/armethaumaturgy/pseuds/armethaumaturgy
Summary: “I bet I can make you come undone without touching you.”Killer cocks his head, regarding Nightmare with a raised brow and an expression of clear skepticism. “What, you really think that?”Nightmare’s bright eyelight darkens with a dangerous glint and his teeth curl up minisculely. “You don’t?”Killer narrows his sockets, and yet yields. “Do your worst.”
Relationships: Sans/Sans (Undertale)
Comments: 2
Kudos: 148





	pampinus

“I bet I can make you come undone without touching you.”

Killer cocks his head, regarding Nightmare with a raised brow and an expression of clear skepticism. “What, you really think that?”

Nightmare’s bright eyelight darkens with a dangerous glint and his teeth curl up minisculely. “You don’t?”

Killer narrows his sockets, and yet yields. “Do your worst,” he taunts, making Nightmare’s face brighten up into a wide smile that would have most monsters’ blood freezing.

Nightmare stands from his throne and motions Killer to take his spot. Killer does, if a little warily; he’d never sat on the thing, and he wouldn’t admit he’d wondered if it was as soft as it looked. It was.

Nightmare raises his hands up, showing his palms for Killer to see. What Killer fails to notice however, keeping all his attention on Nightmare and his movements, is the two bottommost tentacles winding their way across the throne room. They take a detour over the cracks of the wooden floor and besides the fluffy, if neglected and old, carpet, so that they’re not as noticeable.

Killer only — finally — notices them as they wind around his ankle and snake up the throne, taking a hold of his wrists. His first instinct is to break free, but his gaze is still trained on Nightmare, and he has that shit-eating grin on his face, and Killer doesn’t want to give him the satisfaction of showing how off-guard he’d been caught.

If it were anybody else, Killer would already be free and with his knife at their throat, but this is his Nightmare, so he allows the tentacles to tug him up, off the throne, off the ground. Well, that had been short-lived, but at least he’d satisfied one of his curiosities.

The tentacles feel soft, less runny as they glide over his bones, slipping beneath his pants and his sleeves to wind around his limbs to hold him in the air more securely. He twists around, trying to free himself, if only for show, but they don’t budge.

And they’re deft, he finds, as they manage to wiggle his hoodie off of him with minimal effort, somehow not letting him go. Instead one unwinds and the other replaces it, to grab the fabric and carry it over to Nightmare, who takes it in one hand, dropping the other from where it’d still been held up.

The glint in his eyelight is positively dark. He shucks the hoodie onto himself, heedless of the few wet stains left on it here and there, and then plops himself straight back onto the throne, folding his legs and leaning onto one elbow as he looks up at Killer.

“Told you,” he sing-songs.

Killer feels a rush of heat at the sight of him like that, dwarfed by the large, gold-plated seat, with Killer’s hoodie wrapped around him (oh, and it is getting stained by his goop. Killer isn’t sure why he’s finding that hot), and looking like he’d just cheated life. “The tentacles are cheating, don’tya think?” he manages to say, and it only serves to make Nightmare’s expression darker and the tendrils a little tighter around him. “Plus, I’m still very much fine.”

“Oh, don’t worry, Kills,” Nightmare coos, “You’ll be more than done when I’m through with you.”

He doesn’t give Killer much time or chances to reply, instead using the tentacles to branch out, _more_ tendrils winding around Killer’s forearms and tugging them behind his back, effectively rendering them useless. More tendrils seem to split from the already existing ones, branching out and running over hot bone, cooling it with their surfaces.

Killer suppresses a gasp as a tentacle tears his shirt in half, narrowly missing his SOUL and leaving his chest bare. He shivers as the air tickles the wet trails left by the tendrils.

Nightmare must notice this, because not even a moment later, there’s a tendril running down his ribcage, teasingly light over each of his ribs. Killer jerks within the tendrils’ hold, a laugh bubbling up from deep within his chest. It sounds much louder in the giant, mostly-empty throne room than it actually is. Thankfully, there’s no one to hear them, so neither of them worries about keeping quiet.

It’s just a laugh now, but when the tendril presses against the bone just a little firmer, curling inwards and _wrapping_ around the floating ones, the laugh dies out in favor of a soft exhale, the skeleton’s eyesockets fluttering closed as Nightmare starts to tug the lowermost ones.

Nightmare has to take a moment to rearrange himself on the throne, uncrossing and recrossing his legs.

Then he gives all his attention back to Killer and his eagerness as he tries to arch his chest into the touch of the tendrils twisting and winding through his ribs and running over his scar-ridden bones. Tiny rivulets of goo cascade down his stomach cavity and soak into the fabric of his pants.

Nightmare takes mercy on him, slipping a pair of tendrils up from his ankles to his hips, curling around to hold his weight while another pair worms into his pants, yanking them down and off of his legs. They end up in a useless puddle on the ground, all of Killer on display as his joints light up with magic. There’s already a gathering of it in his pelvic inlet, hot and whirling and begging to form.

Nightmare forces down a laugh, moving a tendril to trace the cloud of magic, watching enraptured as it stirs along with the touch and glide of the tendril. Killer grits his teeth as Nightmare makes the tentacle curl through it, fucking it with slow moves. 

His ecto-body snaps into place around it, walls fluttering around the intrusion and dripping with slick that mixes with Nightmare’s goop and slides down his conjured thighs. His cock only adds to the mess, a string of precum rolling down the length only to make him shiver.

The tendril leaves his entrance before he can even enjoy it fully, dragging a line of slick as it curls around the length instead and starts pumping it, black dripping down Killer's thighs in no time at all. He writhes in his restraints, prompting Nightmare to tighten them to make sure he wouldn’t slip free by some miracle that always follows in Killer’s footsteps.

“Hn, Nightmare,” Killer breathes out with the last of the air in his fake-lungs, ribcage stuttering as he gasps for more.

“Weren’t expecting me to be serious, huh?” Nightmare teases, catching Killer’s hazed eyesockets with his narrowed one, his smirk curling his whole face. With one, way too smooth and elegant flick of his wrist, the tendril curled around Killer’s dick squeezes. Almost like a snake, the tighter part moves along the length, around the base one second, around the weeping crown the other.

Killer keens.

“Night—”

“Hush, I didn’t even start yet,” Nightmare chastises. Not that he really wants Killer to be quiet; no, he loves all the little whines and whimpers and gasps and moans of his name. And Killer knows this, so even though he stops trying to string together a sentence, there’s still tiny breathless sounds pouring out.

They’re desperate and open, and Nightmare can taste the plethora of emotions bubbling within Killer’s SOUL on the tip of his tongue, and it’s all so delectable. Who is Nightmare to deny him when he begs so nicely, without even using his words?

He leans his head onto one thin wrist as he regards Killer, contemplating what to do with him. Catching the pleading look in Killer’s eyes, Nightmare comes to a decision. He uses the tendrils wrapped around Killer’s thighs to pull them up and apart, jostling the skeleton into a half-lying position in midair, his lower half on full display.

Nightmare licks his teeth at the sight of the glimmering precum oozing from the red, swollen tip of Killer’s cock, dribbling down and getting eaten up by one of the tendrils as it runs over the flesh. Even lower still, Nightmare’s eyelight trains onto his entrance.

“Hmm,” he hums softly, one tendril unwinding from Killer’s ankle to hover right in front of the twitching lips, in the perfect position for the other to see it bobbing up and down slightly. “Tell me what you want?”

Killer’s browbones visibly draw together and he glares at Nightmare, though the effect is lost when his hips buck up into the tendril around his cock that decides to move again. “You know what I want!” he huffs, trying to twist out of the hold on his arms, but without success.

Nightmare chuckles lightly, “Do I? What if I got it wrong?”

“Gods, Night—!” Killer groans, “Just fuck me!”

Nightmare’s chuckles get louder and he relents the teasing. For now. Instead, the tendril stretches out, becoming thinner as it runs over the swollen lips, adding to the wet mess already dripping down there.

Killer wiggles, trying to push back against it, though he can’t really move. Nightmare motions it to push inside, and it does, so thin that there’s barely any stretch, just Killer breathing out as it rubs against his insides. It’s no thicker than a single finger, but it keeps pushing in, further than any of Nightmare’s fingers or cock ever could, and Killer keens loudly, spine arching splendidly. His head is thrown back and he clenches down on the tendril, claws digging into his own palms.

When it feels like the tendril is already breaching into his stomach and he’s completely out of breath, it pulls out, painfully slowly. It doesn’t pull out completely, but he still feels empty.

Killer’s eyesockets go wide when it pushes back inside, just as slowly and just as deeply, but it’s a little wider this time, stretching his pseudo-muscles a bit more, wracking his body with ceaseless sensations. He almost doesn’t even notice that the tentacle around his cock is still moving, because with each impossibly deep thrust, the tendril inside of him gets just a little bigger, until it’s stretching him wide and it feels like he’s filled to the brim.

“Ah— Night—mare!” Killer cries out, writhing wildly as the pace of the tendril pumping in and out of him quickens, rubbing over his sensitive insides in all the right ways, stretching the velvety walls with its coldness that doesn’t seem to go away, no matter how long the tendril stays inside of him.

“Enjoying yourself? Good,” Nightmare says, not waiting for an answer. Killer’s expression is all the answer he needs. The skeleton moves along with the tendrils, sweat clinging to his bones joints lit up enough to cast shadows over the throne. He looks absolutely delectable.

Deciding to push Killer even further, Nightmare wills one of the tendrils to split again. A tiny one, no bigger than a stem of a dandelion splits from the one around Killer’s cock to thumb at the tip. Killer doesn’t understand what it’s doing until it rubs over the dripping opening of his cock and slithers inside, just as painlessly as the one already inside of him had before.

He screams, voice breaking as his body gets wracked with a shiver, SOUL wavering where it floats. Tingles blossom in his nerves, along his spine, followed by a rush of pleasure that wipes everything from his mind, leaving him seeing white.

“Nightmare!!”

Nightmare feels a pang of pride in his chest, uncrossing his legs again, trying to find a good position. Then he decides, why should he? “Hey, Killer? Are you enjoying yourself?”

Nightmare’s voice pulls Killer’s attention, though it’s probably more because the tendrils stop moving, lodged snugly deep within him. The one inside his cunt is swelled so much that it’s constantly pressing against each spot that sends shivers up his vertebrae, the tip reaching so deep there’s a visible bulge on his abdomen, black peeking under the red ecto. It’s more prominent when he breathes out, ribcage rising and falling frantically.

It obviously takes him a moment to understand that Nightmare is waiting for an answer. When it does, Killer opens his mouth to answer, only to find his voice gone, throat too dry. He takes an extra moment to swallow a few times before he can formulate any words. “Why’d you— stop…?”

“Oh, sorry, sorry,” Nightmare says, not sounding apologetic in the slightest. “Are you enjoying yourself?”

“Yeah,” tumbles from Killer’s teeth immediately, “At least— I was.”

“You sure looked like it.” Even still, there’s a line of spittle running down Killer’s chin, the liquid hate rolling down his cheekbones slowing down to the point of it not dripping down anymore. “I’m feeling a little left out, you know…?” Killer’s gaze strays down to the very obvious bulge in Nightmare’s pants and he licks his lips with even more obvious hunger. Nightmare smiles to himself. “You don’t mind helping me out, do you?”

Killer finds himself nodding without thinking. Nightmare motions the tendrils to bring Killer closer. He ends up on the floor, patella hitting the red carpet softly. The tendrils don’t let go of him, though, keeping just as tight a hold on him as ever.

Nightmare pulls his pants down, sighing out as the strain of the fabric disappears, his arousal bobbing in front of Killer’s face, eyelight following it and the bead of precum gathered at the top.

“Careful of your teeth, okay?” Nightmare mutters, though he isn’t very concerned at this point. They’d done this enough times that Killer just obediently opens his mouth, leaning forward to run his tongue over the hard flesh. Nightmare shivers, looking down and catching Killer’s eyes, looking back up at him. He’s never needed eyelights for Nightmare to know where he was looking.

Nightmare decides that Killer is far gone already, so he has no qualms about placing his hand onto his skull as Killer starts swallowing the head of his cock. Just as the tendrils, even Nightmare’s ecto-flesh is still cold, like a glass of water. Killer’s sharp teeth barely touch the skin, just a tiny warning of what he’s capable of, even if he’d never use it on Nightmare. Nightmare moans lowly.

“Great job, Killer,” he mutters, only half aware of it as Killer’s tongue runs over the crown of his cock, lapping up the precum and swallowing, sending even more spikes of pleasure through Nightmare.

Nightmare rewards him by making the tendrils move again, reveling in the moan Killer lets out around him. The tendril pressed inside Killer splits into two identical ones, Nightmare concentrating as much as he can to wind them around each other. They pump in and out in tandem, one in while the other pulls out, ensuring Killer’s sensitive spots get rubbed with each thrust.

The one inside Killer’s cock moves in tiny thrusts, rubbing against his sensitive flesh from the other side, swelling just enough to be visible on the underside of his cock. Killer bobs his head on Nightmare, taking him as far as he can, lapping at the flesh and leaving kisses along the crown when he pulls away to breathe.

Nightmare feels his orgasm approaching fast, a combination of seeing Killer so vulnerable and debauched and his arousal being neglected for so long rushing it. He grips at Killer’s skull a little tighter, gritting his teeth. He pulls Killer off of himself just enough not to choke him with his cum, enjoying the tiny, kittenish licks as he cums into Killer’s mouth, Killer swallowing it all and looking up with a dazed look, a blush high on his cheekbones.

Panting harshly, Nightmare finally pulls Killer off, moving him with the tentacles so he can kiss him, tasting himself on his tongue but not caring.

“Nightmare—” Killer whimpers when they part, a string of crimson and black connecting their teeth until it snaps into nothingness with Killer’s laboured breathing. “Please— Please, take it out… I want to come…”

Through the haze of his afterglow, Nightmare looks down at the begging skeleton, notes the tears collecting in the corners of his sockets. The tiny tendril pulls out from within his cock with one last teasing flick, and like a dam broken, Killer’s cum follows it, ribbons of it shooting out and painting the throne red.

Killer slumps forward in the tendrils’ hold, boneless and sated. Nightmare carefully pulls the pair of tendrils out of him, mindful not to overwhelm his already overstimulated body. The tendrils pull him up and Nightmare scoops him into his own arms.

The tentacles settle back behind him, waving the barest amount in satisfaction. Killer stretches up to kiss Nightmare again, eyesockets falling shut in exhaustion.

“Told you,” Nightmare chuckles, brushing the sweat and inky mess off his face. “Come on, don’t fall asleep yet, I gotta wash you.”

Killer’s answer is a noncommittal hum, but it only takes a few more seconds before he’s out, leaving Nightmare to carry his lax body to the bathroom with just a sigh.

He did bring it upon himself, he supposes.


End file.
